Process control systems may be implemented to automatically control industrial processes based on pre-defined logic and/or rules. Industrial processes may be carried out by motors, valves, heaters, pumps, and the like, which may be referred to as process devices or field devices, in manufacturing plants, refineries, food processing plants, and other plants. The process control systems may monitor parameters and/or properties of on-going processes by receiving outputs from sensors coupled to the processes, for example temperature sensors, pressure sensors, motion sensors, weight sensors, density sensors, flow rate sensors, and other sensors. Automated control devices, for example controllers, may adjust and control process devices based on the sensed parameters and properties based on pre-defined logic and/or command inputs from, for example, a human machine interface.
Current methodologies for use in control system redundancy commonly include triple modular redundancy (TMR) with voting at all interfaces and/or various Hot Swap methods where an active module controls all processes and a standby module is ready to take over in the event of any failure. TMR approaches typically allow all three legs of the controller to participate in a voted change to the end stations with all members having an equal vote and 2 out of 3 voting to resolve slight timing differences. TMR may verify votes at all endpoints in the system. This may entail tripling at least some hardware components in the controller, increasing cost and customized voting at endpoints increasing end point complexity. Hot swap methods rely on the active device self-diagnosing a fault and shutting down to allow the standby module to be promoted to the active role. Such hot swap methods may entail erroneous values being applied to the process until diagnostics detect a faulty active module, the faulty active module being shut down, and the standby module being promoted to active.
Other current systems can utilize a dual-active approach which does not require end-point voting. For example, two control modules can execute the same sequence of operations and produce the same process settings and/or commands. Settings and/or commands produced by the two control modules can be verified by communications hardware to be in agreement prior to forwarding on to other devices, for example to controlled process devices. In an embodiment, this approach may entail dedicated hardware for synchronization of state, Clock synchronization, and comparison of message content.
The current systems as well as those described herein may be implemented on a processor forming a part of a computer. As will be appreciated by one skilled in the art, computers and computer systems may come in different shapes, sizes, and implements. At the same time, computers and/or computer systems may be said to comprise some common elements and have some common optional elements. For example, a computer system may comprise a processor (which may be referred to as a central processor unit or CPU) that is in communication with memory devices including secondary storage, read only memory (ROM), random access memory (RAM), input/output (I/O) devices, and network connectivity devices. The processor may be implemented as one or more CPU chips.
It is understood that by programming and/or loading executable instructions onto the computer system, at least one of the CPU, the RAM, and the ROM are changed, transforming the computer system in part into a particular machine or apparatus having the novel functionality taught by the present disclosure. It is fundamental to the electrical engineering and software engineering arts that functionality that can be implemented by loading executable software into a computer can be converted to a hardware implementation by well known design rules. Decisions between implementing a concept in software versus hardware typically hinge on considerations of stability of the design and numbers of units to be produced rather than any issues involved in translating from the software domain to the hardware domain. Generally, a design that is still subject to frequent change may be preferred to be implemented in software, because re-spinning a hardware implementation is more expensive than re-spinning a software design. Generally, a design that is stable that will be produced in large volume may be preferred to be implemented in hardware, for example in an application specific integrated circuit (ASIC), because for large production runs the hardware implementation may be less expensive than the software implementation. Often a design may be developed and tested in a software form and later transformed, by well known design rules, to an equivalent hardware implementation in an application specific integrated circuit that hardwires the instructions of the software. In the same manner as a machine controlled by a new ASIC is a particular machine or apparatus, likewise a computer that has been programmed and/or loaded with executable instructions may be viewed as a particular machine or apparatus.
The secondary storage is typically comprised of one or more disk drives or tape drives and is used for non-volatile storage of data and as an over-flow data storage device if RAM is not large enough to hold all working data. Secondary storage may be used to store programs which are loaded into RAM when such programs are selected for execution. The ROM is used to store instructions and perhaps data which are read during program execution. ROM is a non-volatile memory device which typically has a small memory capacity relative to the larger memory capacity of secondary storage. The RAM is used to store volatile data and perhaps to store instructions. Access to both ROM and RAM is typically faster than to secondary storage. The secondary storage, the RAM, and/or the ROM may be referred to in some contexts as computer readable storage media and/or non-transitory computer readable media.
I/O devices may include printers, video monitors, liquid crystal displays (LCDs), touch screen displays, keyboards, keypads, switches, dials, mice, track balls, voice recognizers, card readers, paper tape readers, or other well-known input devices.
The network connectivity devices may take the form of modems, modem banks, Ethernet cards, universal serial bus (USB) interface cards, serial interfaces, token ring cards, fiber distributed data interface (FDDI) cards, wireless local area network (WLAN) cards, radio transceiver cards such as code division multiple access (CDMA), global system for mobile communications (GSM), long-term evolution (LTE), worldwide interoperability for microwave access (WiMAX), and/or other air interface protocol radio transceiver cards, and other well-known network devices. These network connectivity devices may enable the processor to communicate with the Internet or one or more intranets. With such a network connection, it is contemplated that the processor might receive information from the network, or might output information to the network in the course of performing the above-described method steps. Such information, which is often represented as a sequence of instructions to be executed using processor, may be received from and outputted to the network, for example, in the form of a computer data signal embodied in a carrier wave.
Such information, which may include data or instructions to be executed using processor for example, may be received from and outputted to the network, for example, in the form of a computer data baseband signal or signal embodied in a carrier wave. The baseband signal or signal embodied in the carrier wave generated by the network connectivity devices may propagate in or on the surface of electrical conductors, in coaxial cables, in waveguides, in an optical conduit, for example an optical fiber, or in the air or free space. The information contained in the baseband signal or signal embedded in the carrier wave may be ordered according to different sequences, as may be desirable for either processing or generating the information or transmitting or receiving the information. The baseband signal or signal embedded in the carrier wave, or other types of signals currently used or hereafter developed, may be generated according to several methods well known to one skilled in the art. The baseband signal and/or signal embedded in the carrier wave may be referred to in some contexts as a transitory signal.
The processor executes instructions, codes, computer programs, scripts which it accesses from hard disk, floppy disk, optical disk (these various disk based systems may all be considered secondary storage), ROM, RAM, or the network connectivity devices. While only one processor is shown, multiple processors may be present. Thus, while instructions may be discussed as executed by a processor, the instructions may be executed simultaneously, serially, or otherwise executed by one or multiple processors. Instructions, codes, computer programs, scripts, and/or data that may be accessed from the secondary storage, for example, hard drives, floppy disks, optical disks, and/or other device, the ROM, and/or the RAM may be referred to in some contexts as non-transitory instructions and/or non-transitory information.
In an embodiment, the computer system may comprise two or more computers in communication with each other that collaborate to perform a task. For example, but not by way of limitation, an application may be partitioned in such a way as to permit concurrent and/or parallel processing of the instructions of the application. Alternatively, the data processed by the application may be partitioned in such a way as to permit concurrent and/or parallel processing of different portions of a data set by the two or more computers. In an embodiment, virtualization software may be employed by the computer system to provide the functionality of a number of servers that is not directly bound to the number of computers in the computer system. For example, virtualization software may provide twenty virtual servers on four physical computers. In an embodiment, the functionality disclosed above may be provided by executing the application and/or applications in a cloud computing environment. Cloud computing may comprise providing computing services via a network connection using dynamically scalable computing resources. Cloud computing may be supported, at least in part, by virtualization software. A cloud computing environment may be established by an enterprise and/or may be hired on an as-needed basis from a third party provider. Some cloud computing environments may comprise cloud computing resources owned and operated by the enterprise as well as cloud computing resources hired and/or leased from a third party provider.
In an embodiment, some or all of the functionality disclosed above may be provided as a computer program product. The computer program product may comprise one or more computer readable storage medium having computer usable program code embodied therein to implement the functionality disclosed above. The computer program product may comprise data structures, executable instructions, and other computer usable program code. The computer program product may be embodied in removable computer storage media and/or non-removable computer storage media. The removable computer readable storage medium may comprise, without limitation, a paper tape, a magnetic tape, magnetic disk, an optical disk, a solid state memory chip, for example analog magnetic tape, compact disk read only memory (CD-ROM) disks, floppy disks, jump drives, digital cards, multimedia cards, and others. The computer program product may be suitable for loading, by the computer system, at least portions of the contents of the computer program product to the secondary storage, to the ROM, to the RAM, and/or to other non-volatile memory and volatile memory of the computer system. The processor may process the executable instructions and/or data structures in part by directly accessing the computer program product, for example by reading from a CD-ROM disk inserted into a disk drive peripheral of the computer system. Alternatively, the processor may process the executable instructions and/or data structures by remotely accessing the computer program product, for example by downloading the executable instructions and/or data structures from a remote server through the network connectivity devices. The computer program product may comprise instructions that promote the loading and/or copying of data, data structures, files, and/or executable instructions to the secondary storage, to the ROM, to the RAM, and/or to other non-volatile memory and volatile memory of the computer system.
In some contexts, a baseband signal and/or a signal embodied in a carrier wave may be referred to as a transitory signal. In some contexts, the secondary storage, the ROM, and the RAM may be referred to as a non-transitory computer readable medium or a computer readable storage media. A dynamic RAM embodiment of the RAM, likewise, may be referred to as a non-transitory computer readable medium in that while the dynamic RAM receives electrical power and is operated in accordance with its design, for example during a period of time during which the computer is turned on and operational, the dynamic RAM stores information that is written to it. Similarly, the processor may comprise an internal RAM, an internal ROM, a cache memory, and/or other internal non-transitory storage blocks, sections, or components that may be referred to in some contexts as non-transitory computer readable media or computer readable storage media.